Metacentric height (GM)
Abbreviation: GM
The distance between the centre of gravity (G) and the metacentre (M) — the primary indicator of transverse initial stability.
Regulatory detail & full definition
GM (metacentric height) is the vertical distance between G (centre of gravity) + M (metacentre). A positive GM means the ship rights itself when heeled; a negative GM (rare, dangerous) means the ship is unstable. Typical merchant-ship GM 0.15-1.5 m — too high = stiff + uncomfortable rolling; too low = tender + long roll period. Chief Officer computes GM every voyage using the ship's loading computer + stability booklet. See /glossary/km-metacentric-height-from-keel for the KM component.
Authoritative source: IMO — Intact Stability ↗
Related
Source: IMO Intact Stability Code
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